AM_Armstrongite
Formula: Ca Zr Si6 O17 H4
Name: Armstrongite
Unit cell: 14.04 14.16 7.81 90.0 109.55 90.0 , V=1463.17
Space group: C121 (5)

Kashaev A A , Sapozhnikov A N , Kristallografiya , 23 (1978) p.956-961, Crystal structure of armstrongite